Guidewire having braided wire over drawn tube construction

ABSTRACT

An intracorporeal device, preferably a guidewire, and method of making same that has an elongate inner core element with an outer layer of material disposed about the core element. The layer of material can be applied as a braid, strand or smooth layer of material, and is preferably a metal. If the layer of material is applied as a braid or strand, it may be subsequently cold drawn so as to create a smooth layer from the braid or strand. The inner core element may be homogeneous, or may consist of drawn filled tubing with at least two layers of material, preferably biocompatible metals. In this way, the multiple layer distal section of the elongate core can be shaped or ground so as to achieve the desired mechanical properties and provide surfaces for attachment of components that are readily bonded or soldered to.

BACKGROUND OF THE INVENTION

This invention relates to the field of guidewires for advancingintraluminal devices such as stent delivery catheters, balloondilatation catheters, atherectomy catheters and the like within bodylumens.

Conventional guidewires for angioplasty and other vascular proceduresusually comprise an elongated core member with one or more taperedsections near the distal end thereof and a flexible body such as ahelical coil disposed about the distal portion of the core member. Ashapable member, which may be the distal extremity of the core member ora separate shaping ribbon which is secured to the distal extremity ofthe core member extends through the flexible body and is secured to arounded plug at the distal end of the flexible body.

In a typical coronary procedure, a guiding catheter having a preformeddistal tip is percutaneously introduced into a patient's peripheralartery, e.g. femoral or brachial artery, by means of a conventionalSeldinger technique and advanced therein until the distal tip of theguiding catheter is seated in the ostium of a desired coronary artery. Aguidewire is positioned within an inner lumen of a dilatation catheterand then both are advanced through the guiding catheter to the distalend thereof. The guidewire is first advanced out of the distal end ofthe guiding catheter into the patient's coronary vasculature until thedistal end of the guidewire crosses a lesion to be dilated, then thedilatation catheter having an inflatable balloon on the distal portionthereof is advanced into the patient's coronary anatomy over thepreviously introduced guidewire until the balloon of the dilatationcatheter is properly positioned across the lesion. Once in positionacross the lesion, the procedure is performed.

A requirement for guidewires is that they have sufficient columnstrength to be pushed through a patient's vascular system or other bodylumen without kinking. However, they must also be flexible enough toavoid damaging the blood vessel or other body lumen through which theyare advanced. Efforts have been made to improve both the strength andflexibility of guidewires to make them more suitable for their intendeduses, but these two properties are for the most part diametricallyopposed to one another in that an increase in one usually involves adecrease in the other.

Further details of guidewires, and devices associated therewith forvarious interventional procedures can be found in U.S. Pat. No.4,748,986 (Morrison et al.); U.S. Pat. No. 4,538,622 (Samson et al.):U.S. Pat. No. 5,135,503 (Abrams); U.S. Pat. No. 5,341,818 (Abrams etal.); and U.S. Pat. No. 5,345,945 (Hodgson et al.) which are herebyincorporated herein in their entirety by reference thereto.

Pseudoelastic alloys can be used to achieve both flexibility andstrength. When stress is applied to NiTi alloy exhibiting pseudoelasticcharacteristics at a temperature at or above which the transformation ofmartensite phase to the austenite phase is complete, the specimendeforms elastically until it reaches a particular stress level where thealloy then undergoes a stress-induced phase transformation from theaustenite phase to the martensite phase. As the phase transformationproceeds, the alloy undergoes significant increases in strain but withlittle or no corresponding increases in stress. The strain increaseswhile the stress remains essentially constant until the transformationof the austenite phase to the martensite phase is complete. Thereafter,further increase in stress are necessary to cause further deformation.

If the load on the specimen is removed before any permanent deformationhas occurred, the martensitic specimen will elastically recover andtransform back to the austenite phase. The reduction in stress firstcauses a decrease in strain. As stress reduction reaches the level atwhich the martensite phase transforms back into the austenite phase, thestress level in the specimen will remain essentially constant until thetransformation back to the austenite phase is complete, i.e. there issignificant recovery in strain with only negligible corresponding stressreduction. After the transformation back to austenite is complete,further stress reduction results in elastic strain reduction. Thisability to incur significant strain at relatively constant stress uponthe application of a load and to recover from the deformation upon theremoval of the load is commonly referred to as pseudoelasticity. Theseproperties to a large degree allow a guidewire core of a psuedoelasticmaterial to have both flexibility and strength. However, psuedoelasticalloy components are typically difficult to join or secure to othercomponents. This is due primarily to a tenacious oxide layer thatdevelops on the surface of some such alloys, particularly thosecontaining titanium.

Prior methods of pre-treatment for securing subassemblies to a distalcore made of pseudoelastic alloys such as NiTi include molten or fusionsalt etching and then pre-tinning the core to facilitate forming astrong bond, as seen in U.S. Pat. No. 5,695,111 to Nanis et al. which ishereby incorporated in its entirety by reference. While this methodrepresents a significant advance, what has been needed is a method formanufacturing a guidewire with a superelastic or psuedoelastic componentwhich will allow the component to accept a weld, solder or adhesivejoint with ease of manufacture and low cost. It is also desirable tohave a manufacturing process in which the mechanical properties ofpsuedoelastic and high strength alloys can be combined.

SUMMARY OF THE INVENTION

The present invention is directed to an intracorporeal device,preferably a guidewire, and method for making the device. The guidewirehas an elongate core member with a proximal section and a distalsection. The elongate core has an inner core element of a desired metaland an outer layer of material disposed about the inner core element.The outer layer of material is typically applied to the inner coreelement as a braid which is then cold drawn through a die which conformsand secures the outer layer to the inner core element. The outer layerof material may be cold drawn to a smooth continuous layer, or may becold drawn to a lesser extent where the outer layer maintains a braidedflattened configuration.

In an alternative embodiment of the invention, an elongate core memberhas a second outer layer of material applied to an inner core elementand a first outer layer of material which may be drawn filled tubing.The drawn filled metallic tubing preferably consists of an inner coreelement of stainless steel and a first outer layer of psuedoelasticalloy, normally consisting of NiTi alloy disposed about the inner coreelement. The second outer layer of braided stainless steel is appliedand cold drawn through a die so as to create an elongate core memberhaving a layer of NiTi alloy sandwiched between an inner core elementand an outer layer of stainless steel. When the distal section of thiselongate core member is tapered to a distally smaller cross section, thevarious layers of the elongate core member are exposed.

Typically, a flexible body is disposed over and secured to at least aportion of the distal section of the elongate core member. The flexiblebody can be a helical spring but can also be a polymer jacket ofmaterial that can be thin or sufficiently thick to provide a diametersimilar to that of the proximal section.

The distal end of the helical coil, or other flexible body, ispreferably secured to a distal end of the elongated core member, bysoldering, brazing, welding, bonded polymeric materials or othersuitable means.

The inner core element, which is preferably stainless steel or othersuitable high strength bondable or solderable material, is exposed atthe distal end of the elongate core member as a result of the taperingof the distal section. Exposure of the inner core element allows thedistal end of the flexible body to be bonded or soldered to the distalend of the bondable or solderable material of the inner core element. Aproximal end of the flexible body is preferably bonded or soldered to adistal section of the second outer layer of material. Preferably, thesecond outer layer of material is comprised of stainless steel or someother suitable bondable or solderable material. In this way, theflexible body will have its distal and proximal ends secured to bondableor solderable materials. If the first outer layer of material is made ofa pseudoelastic alloy, a desired amount of the distal section canexhibit mechanical properties of the pseudoelastic alloy which comprisesthe majority of the distal section material. This results in highstrength bonding or soldering between the guidewire components, smoothflexibility transitions in the elongate core member and the desiredpseudoelastic mechanical characteristics in the distal section of theelongate core member. In addition to solderability and bondability, theouter layers of material may be selected for desired mechanical strengthproperties. For example, a second outer layer of material may be madefrom a precipitation hardenable alloy such as MP35N in order to give theproximal section of the elongate core member a desired amount ofstrength.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a longitudinal cross sectional view of a guidewire havingfeatures of the invention.

FIG. 2 is a transverse cross sectional view of the guidewire of FIG. 1taken at lines 2--2 in FIG. 1.

FIG. 3 is a transverse cross sectional view of the guidewire of FIG. 1taken at lines 3--3 in FIG. 1.

FIG. 4 is a schematic view of an outer layer of material being braidedonto an inner core element and cold drawn.

FIG. 5 is a transverse cross sectional view of the outer layer ofmaterial and inner core element of FIG. 4 taken at lines 5--5 in FIG. 4.

FIG. 6 is a transverse cross sectional view of a stranded outer layer ofmaterial over an inner core element.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a longitudinal cross sectional view of a guidewire 10 havingfeatures of the invention. An elongate core member 11 has an inner coreelement 12, a first outer layer of material 13 disposed on an outersurface 14 of the inner core element, and a second outer layer ofmaterial 15 disposed on an outer surface 16 of the first outer layer ofmaterial. The first outer layer of material 13 and second outer layer ofmaterial 15 are shown as smooth continuous layers. The inner coreelement 12 has a proximal section 17, a distal section 18 and a distalend 21. The second outer layer 15 has a proximal section 22 and a distalsection 23. A distal section 24 of the elongate core member 11 has adistally tapered segment 25 which can be adjusted in length, taper angleand cross sectional shape to achieve the desired flexibility andperformance characteristics for the guidewire 10. The distally taperedsegment 25 also serves to expose the distal end 21 of the inner coreelement 12 to which a distal end 26 of a flexible body 27 is secured.The distal end 26 of the flexible body 27 is secured to the distal end21 of the inner core element 12 by a first body of solder 28. A proximalend 31 of the flexible body 27 is secured to the distal section 23 ofthe second outer layer of material 15 with a second body of solder 32.Although a single distally tapered segment 25 is shown, the distalsection 24 of the elongate core member 11 may have two or more suchtapered segments which may or may not be separated by segments ofsubstantially constant diameter.

A flexible body 27, such as a helical coil, polymer jacket, or the like,surrounds and covers at least a portion of the distal section 24 of theelongate core member 11. Polymers suitable for forming a flexible body27 can include polyimide, polyethylene, polyurethane, TFE, PTFE, ePTFEand other similar materials. A flexible body 27 in the form of a helicalcoil may be formed of a suitable radiopaque material such as tantalum,gold, iridium, platinum or alloys thereof or formed of other materialsuch as stainless steel and coated with a radiopaque material such asgold. The wire from which the coil is made generally has a transversediameter of about 0.001 to about 0.004 inch, preferably about 0.002 toabout 0.003 inch (0.05 mm). Multiple turns of a distal portion of coil27 may be expanded to provide additional flexibility. The helical coil27 may have transverse dimensions about the same as a proximal coresection 35. The coil 27 may have a length of about 2 to about 40 cm ormore, but typically will have a length of about 2 to about 10 cm inlength.

The inner core element 12 and second outer layer of material 15 are madeof stainless steel but can also be made of any other suitable solderableor bondable high strength materials. The first outer layer of material13 disposed between the inner core element 12 and the second outer layerof material 15 is a pseudoelastic alloy, more specifically, NiTi alloy,which is chosen for its mechanical properties and performance. The firstouter layer of material may also be made of any suitable metal or alloyhaving desired properties. The inner core element 12, first outer layerof material 13, and second outer layer of material 15 may be formed ofstainless steel, NiTi alloys, MP35N, L605 or combinations thereof suchas described in U.S. Pat. No. 5,341,818 (Abrams et al) which isincorporated herein in its entirety. Other materials such as the highstrength alloys as described in U.S. Pat. No. 5,636,641 (Fariabi),entitled HIGH STRENGTH MEMBER FOR INTRACORPOREAL USE, which isincorporated herein by reference, may also be used.

As is known in the art, many materials used for guidewire constructionhave desirable mechanical properties, but are difficult to assemble toother guidewire components using conventional technology such assoldering or use of polymer adhesives due to inherent surface propertiessuch as tenacious oxide layers. The construction shown in FIG. 1 allowsthe use of materials which have poor bondability or solderability, suchas NiTi alloy in a guidewire core without concern for the bondability orsolderability of the material.

FIG. 2 shows a transverse cross sectional view of the guidewire 10 ofFIG. 1 taken at lines 2--2 in FIG. 1. The inner core element 12 issurrounded by a substantially coaxial or concentric first outer layer ofmaterial 13. The first outer layer of material 13 is surrounded by asecond outer layer of material 15. The inner core element has a nominaltransverse dimension of up to about 0.02 inches, preferably about 0.005to about 0.01 inches more preferably about 0.006 to about 0.008 inches.The first outer layer of material 13 and second outer layer of material15 have a nominal wall thickness of up to about 0.015 inches, preferablyabout 0.0005 to about 0.01 inches, and more preferably about 0.001 toabout 0.003 inches. Although the inner core element 12 is shown assolid, the inner core element may also be hollow with a lamen extendinglongitudinally therethrough. A lamen extending longitudinally throughthe inner core element 12 could be used for delivery of diagnostic ortherapeutic agents, such as radioactive therapy agents or growth factorsor the like. The lamen may also be used for advancement of elongatedmedical devices into a patient's vascalature.

FIG. 3 shows a transverse cross sectional view of the guidewire 10 ofFIG. 1 taken at lines 3--3 in FIG. 1. The flexible body 27 is disposedpartially about a distal segment 33 of the elongate core member 11.Referring back to FIG. 1, distal segment 33 is configured to provide ahighly flexible segment at a distal end 34 of the guidewire 10 in orderto facilitate advancement through a patient's vasculature withoutcausing injury thereto. The distal segment 33 is shown as a flattenedportion of the exposed inner core element 12 which facilitatesshapeability of the distal segment, however, the flexible segment canhave a round cross section, or any other suitable configuration.

FIG. 4 illustrates a portion of a method having features of theinvention used to produce an elongate core member 40. An outer layer ofmaterial 41 is being braided onto an outer surface 42 of an inner coreelement 43. The inner core element 43 and outer layer of braidedmaterial 41 are drawn through a die 44 so as to compress the outer layerof braided material onto the outer surface 42 of the inner core elementand produce a smooth coaxial layer of material thereon. The outer layer41 may be cold drawn or co-drawn down to a smooth continuous layer, ormay be partially cold drawn or co-drawn to a lesser extent where theouter layer retains a braided or stranded character that has beenflattened against the outer surface of the inner core member 42. It isdesirable for the cold drawing or co-drawing process to create a bondbetween the inner core member 43 and outer layer of material 41. Thebond between the inner core member 43 and outer layer of material 41 canbe partially or wholly mechanical. As used herein, the term braid orbraided is intended to refer to the process or object resulting from theprocess of interweaving filaments 45 of material such that theindividual filaments overlap each other at regular intervals or pickpoints 46. Such a braid can be produced in a cylindrical configurationby itself, or it can be formed over a mandrel such as the inner coreelement 43. A braid can be defined by the number of filaments 45, thetransverse dimension of the filaments, the transverse dimension of themandrel over which the braid is formed and the picks 46 per unit lengthas the braid is laid down. The term strand or stranded is intended torefer to the process or object resulting from the process of layingfilaments of material in a single layer without overlap of thefilaments. The filaments 45 of an outer layer of material 41 may all beof the same material or may be from a variety of different materials.For example, filaments 45 may all be stainless steel, or some may bestainless steel and others MP35N or NiTi alloy. Filaments of radiopaquematerials such as gold, platinum, tantalum and the like may also beused.

FIG. 5 shows a transverse cross sectional view of the inner core element43 and outer layer of material 41 after passing through the die 44. Theinner core element 43 is shown as solid and non-layered, however, theinner core element may have multiple layers prior to the application ofthe outer layer of braided material 41. The multiple layering of theinner core element 43 may be achieved by the braiding and drawingthrough a die as discussed above, or the layers may be achieved byconventional drawn filled tubing techniques which are known in the art.In addition, the method depicted in FIG. 5 which shows an outer layer ofmaterial 41 applied as braid may also be achieved by applying the layerof material as a strand or other suitable configuration. An elongatecore member 40 having four, five, six or more layers can be achieved byusing the above described methods.

FIG. 6 shows a transverse cross section of an elongate core member 50having an inner core element 51 and an outer layer of material 52. Theouter layer of material 52 has been applied as a strand and partiallycold drawn or co-drawn and retains a stranded character. The outer layerof material 52 has been flattened against an outer surface 53 of theinner core element 51 and is at least partially mechanically securedthereto. Individual filaments 54 can be seen in the outer layer ofmaterial 52.

While particular forms of the invention have been illustrated anddescribed, it will be apparent that various modifications can be madewithout departing from the spirit and scope of the invention.Accordingly, it is not intended that the invention be limited, except asby the appended claims.

What is claimed is:
 1. A guidewire for intraluminal advancement of amedical device within a patient, comprising:a) an elongate core memberhaving a proximal section, a distal section, an inner core element, afirst outer layer of material disposed about an outer surface of theinner core, and a second outer layer of metallic material disposed aboutan outer surface of the first layer of material; and b) a flexible bodydisposed about and secured to at least a portion of the distal sectionof the elongate core member.
 2. The guidewire of claim 1 wherein theinner core element and second outer layer of material are comprised ofstainless steel and the first outer layer of material is comprised of apseudoelastic alloy.
 3. The guidewire of claim 4 wherein the first outerlayer of material is comprised of NiTi.
 4. The guidewire of claim 1wherein the distal section of the elongate core member further comprisesat least one distally tapered portion.
 5. The guidewire of claim 1wherein the flexible body member further comprises a proximal end and adistal end and the proximal end of the flexible body member is securedto a distal section of the second outer layer of material and the distalend of the flexible body member is secured to a distal end of the innercore element.
 6. The guidewire of claim 1 wherein the second outer layerof material is braided.
 7. The guidewire of claim 1 wherein the secondouter layer of material is stranded.
 8. The guidewire of claim 1 whereinthe second outer layer of material is a smooth continuous coaxial layer.9. The guidewire of claim 1 wherein the inner core element has a nominaltransverse dimension of up to about 0.02 inches.
 10. The guidewire ofclaim 1 wherein the inner core element has a nominal transversedimension of about 0.005 to about 0.01 inches.
 11. The guidewire ofclaim 1 wherein the first outer layer of material has a wall thicknessof about 0.0005 to about 0.01 inches.
 12. The guidewire of claim 1wherein the second outer layer of material has a wall thickness of about0.0005 to about 0.01 inches.
 13. The guidewire of claim 1 wherein theinner core element is comprised of MP35N alloy.
 14. The guidewire ofclaim 1 wherein the first outer layer of material is comprised of MP35Nalloy.
 15. The guidewire of claim 1 wherein the second outer layer ofmaterial is comprised of MP35N alloy.